DE102020205680A1 - Method for determining a minimum width and an attachment position of a microjoint and method for machining a workpiece - Google Patents

Abstract

The invention relates to a method for determining a minimum width (BMJ, min) of a microjoint (17), by means of which a workpiece part (14) remains connected to a remaining workpiece (15) of the workpiece (8) when machining an in particular plate-shaped workpiece (8) . In the process, the minimum width (BMJ, min) of the microjoint (17) is determined as a function of at least one machining parameter (p) which, when machining the workpiece (8), defines a relative position of the workpiece part (14) to the remaining workpiece (15) influenced. The invention also relates to a method for determining an attachment position (m) of such a microjoint (17) as well as a method for processing an in particular plate-shaped workpiece (8).

Description

The present invention relates to a method for determining a minimum width of a microjoint, by means of which a workpiece part remains connected to a remaining workpiece of the workpiece when a workpiece, in particular a plate-shaped workpiece, is machined. The invention also relates to a method for determining an attachment position of such a microjoint and a method for machining an in particular plate-shaped workpiece, the method comprising: machining the workpiece with the formation of at least one microjoint through which a workpiece part remains connected to a remaining workpiece.

Microjoints are holding bars between workpiece parts and a remainder of the workpiece, which is sometimes also referred to as scrap skeleton in the following. Microjoints are mainly used when laser cutting or punching, in particular, plate-shaped workpieces in order to keep otherwise separated workpiece parts tilt-free in the scrap skeleton and in this way, for example, to prevent collisions between the processing head during workpiece processing and the workpiece part. Microjoints also simplify the automatic unloading of the workpiece parts together with the scrap skeleton.

The holding webs or the microjoints are created by not cutting or punching the outer contour of the workpiece part all the way to the end. Small retaining bars with a width of a few tenths of a millimeter to one millimeter (so-called microjoints) are set by the programmer of the control program for the processing machine, for example a laser cutting system, either manually or using a set of rules contained in the programming software. The size and the attachment position of the microjoint along the outer contour of the workpiece part usually has to be determined by the programmer. In most cases, all microjoints placed on a plate-shaped workpiece are of the same width, regardless of the process conditions, workpiece part properties (weight, geometry), material, etc.

As a result, microjoints on small workpiece parts tend to be too wide and the small workpiece parts can therefore only be removed from the scrap skeleton with great difficulty. In addition, the reworking necessary to remove the microjoints that are too wide is time-consuming. In general, the wider the microjoint, the greater the reworking required to remove marks on the cutting or punching edge. On large workpiece parts, on the other hand, the microjoint set by the programmer cannot be wide enough so that the workpiece part is not securely held in the scrap skeleton and a collision between the tilted workpiece part and the machining head can result.

From JPH0663659A it is known to calculate the optimal width of a microjoint as a function of the workpiece thickness, the length and the physical properties of the workpiece material and the area of the separated workpiece part. From JPH0439706A it is known to automatically read out an optimal microjoint width, which depends on the material and the thickness of the workpiece, from a parameter database.

Object of the invention

The invention is based on the object of specifying a method for determining a minimum width of a microjoint, an attachment position of a microjoint and a method for machining a workpiece, in which the microjoint has an optimal width.

Subject of the invention

According to a first aspect, this object is achieved by a method of the type mentioned in the introduction, in which the minimum width of the microjoint is determined as a function of at least one machining parameter that influences a relative position of the workpiece part to the remaining workpiece during machining of the workpiece.

The inventors have recognized that to determine an optimized microjoint width, not only parameters of the workpiece part or workpiece part information have to be taken into account - as in JPH0663659A - but also machining parameters of a process or a machining method in which the workpiece part is formed (typically cut or punched) or manipulated (e.g. moved). The at least one machining parameter typically influences a relative position or a relative position of the workpiece part to the remaining workpiece when machining the workpiece. If the minimum permissible width of the microjoint is not reached, reliable processing of the workpiece is no longer possible, since the workpiece part connected to the remaining workpiece via the microjoint with components of a Processing machine, for example with a processing nozzle, can collide or possibly get caught with the remaining workpiece.

The machining parameters can be, for example, the cutting gas pressure acting on the workpiece part during laser cutting, the acceleration and / or static friction when moving the workpiece part together with the remaining workpiece along a workpiece support, vibrations during a combined punch-laser machining of the workpiece, etc. . Act.

The minimum width of the microjoint is determined before the workpiece is machined. The at least one machining parameter that influences the relative position is stored, for example, in a programming system for creating the control programs for machining workpiece parts and is therefore known in advance so that the minimum width of the microjoint can be determined before machining the workpiece.

In addition to the at least one machining parameter, the width of the microjoint is also determined as a function of workpiece information. The workpiece information can be the workpiece material, physical workpiece properties (e.g. E-modulus and yield point of the material), the allocation (nesting) of the plate-shaped workpiece with workpiece parts to be formed during cutting, workpiece part information, etc. Examples of workpiece part information are: geometry of the workpiece part, weight of the workpiece part, position of the workpiece part on the workpiece as well as relative to the support bars of the workpiece support (lying polygon), acting weight force, etc.

Using this workpiece information in the programming system for creating the control programs for cutting the workpiece parts, it is possible to calculate the width of a microjoint depending on the distance of the microjoint from the center of gravity of the workpiece part in such a way that the microjoint prevents the workpiece part from being affected by the weight force Remaining workpiece tilted. For this purpose, the moment acting on the microjoint due to the weight of the workpiece part must not be so great that the yield point of the microjoint is exceeded.

In the calculation, it can be taken into account that the microjoint is elastically and plastically deformed by the force of the workpiece part. The larger the width of the microjoint, the less pronounced the workpiece part typically tilts. In the case of a processing machine, for example in the form of a laser cutting machine, the maximum permissible standing height of the workpiece part when tilting must be smaller than the distance between the processing nozzle of the laser cutting head and the workpiece. In practice, this distance is usually in the value range between 0.4 mm - 1 mm. From this maximum permissible standing height and the geometry of the workpiece part, the maximum permissible tilt angle α _{max of} the workpiece part can be calculated. From the maximum tilt angle α _{max it} follows for the width B _{MJ of} the microjoint: $${\mathrm{B.}}_{\mathrm{M.}J}\ge \sqrt[3]{\frac{1}{{\alpha }_{max}}}$$

The above calculation is sufficient if the cutting end of the outer contour of the workpiece part lies at the microjoint, i.e. the microjoint is formed by the (outer) contour not being completely cut to the end. In this case, the force of the cutting gas acting on the workpiece part at the point of the microjoint due to the gas pressure of the cutting gas exiting the machining nozzle plays only a minor role at the end of the cut, since the workpiece part is held at this point by the microjoint.

In a variant of the method described above, the processing of the workpiece includes thermal cutting of the workpiece with a processing beam, in particular with a laser beam, the minimum width of the at least one microjoint depending on a processing parameter in the form of a cut-off of the workpiece part from the remaining workpiece the gas pressure of a cutting gas exiting from a machining nozzle acting on the workpiece part is determined.

In this variant, the gas flow typically acts on the workpiece part along the outer contour at a free cutting position that is spaced apart from the microjoint. The free cutting position is understood to mean that position along the outer contour of the workpiece part at which the end of the cut lies. After reaching the free cutting position, there is generally no further cutting machining along the outer contour of the workpiece part.

If the microjoint is set at a point on the outer contour that does not correspond to the free cutting position / the end of the cut, the gas pressure of the cutting gas acts on the workpiece part at this free cutting position at the moment the outer contour is closed at the end of the cut. Depending on how the workpiece part is arranged relative to the supporting workpiece support elements (support bars, support slides, ...), there may be areas of the outer contour where the gas pressure of the cutting gas at the free cutting position causes the workpiece part to tilt.

In a further development, a minimum width of the microjoint is determined at which, when the workpiece part tilts relative to the remaining workpiece due to the action of the gas pressure on the workpiece part, a maximum height at which the workpiece part protrudes over the remaining workpiece is not exceeded. In this case, the (minimum) width of the microjoint is so large that the standing height of the tilting workpiece part does not exceed a specified maximum height.

In an advantageous development, the maximum standing height is not greater than a distance between the processing nozzle and the remaining workpiece, the distance preferably being less than 2 mm, particularly preferably less than 1 mm. In this case, the minimum width of the microjoint is determined in such a way that a collision of the upright workpiece part with the processing nozzle of the laser cutting head is prevented. The distance is typically determined between the end face of the machining nozzle and the remaining workpiece.

In a further variant, the processing of the workpiece includes moving the remaining workpiece together with the workpiece part along a workpiece support, the minimum width of the at least one microjoint being determined as a function of at least one processing parameter in the form of an acceleration of the remaining workpiece when moving along at least one displacement direction. The acceleration along a respective displacement direction typically corresponds to an axis parameter of a drive of a processing machine, which is designed to move the remaining workpiece together with the workpiece part along the respective axis or displacement direction.

The workpiece support can have workpiece support elements, for example in the form of balls, brushes or the like, in order to reduce the friction when moving the remaining workpiece with the workpiece part connected via the at least one microjoint along the workpiece support. As a rule, there are areas between the workpiece support elements along the workpiece support in which the workpiece or the workpiece part held by the microjoint is not supported. When moving a workpiece part held by a microjoint on the workpiece support, as is the case with sheetmover machines (e.g. punching or punch-laser combination machines), the weight force acts on the workpiece part in the Z direction if the workpiece part is in a non-supporting area Workpiece support traversed. In addition, the workpiece part is bent around the microjoint in the X-Y plane. The minimum width of the microjoint is therefore also due to the fact that the bending of the microjoint is not so strong that the workpiece part slips under or over the remaining workpiece.

In a further variant, a minimum width of the microjoint is determined at which, when the workpiece part is moved together with the remaining workpiece, a bending stress on the microjoint does not exceed a maximum bending stress. The value for the maximum bending stress is typically set in such a way that the workpiece part does not slip under or over the remaining workpiece when it is moved along the workpiece support.

The maximum bending stress at the microjoint is preferably not greater than a yield point of the material of the workpiece. For the purposes of this application, the 0.2% yield point R _p0.2 (elastic limit) is understood as the yield point, since this (in contrast to the yield point) can always be clearly determined from the nominal stress / total elongation diagram. If the yield point of the material of the workpiece is exceeded, the microjoint is plastically deformed during bending, so that the workpiece part typically remains permanently in a tilted position relative to the rest of the workpiece.

In a further development of this variant, the minimum width of the microjoint is composed of the minimum width of the microjoint at which the maximum bending stress is not exceeded, and a safety factor, the safety factor preferably being dependent on the minimum width of the microjoint at which the maximum bending stress is not exceeded. In this development, an empirically determined safety factor is added to the calculated minimum width of the microjoint, which counteracts the influence of external disturbances, such as vibrations during the punching process, sagging of the workpiece part, deflection of the workpiece part when it passes over support elements (e.g. balls or brushes). considered. In addition, the safety factor can take into account the notch effect occurring at the attachment position of the microjoint due to the sudden diameter reduction, which leads to a reduction in the maximum permissible bending stress. The safety factor is ideally dependent on the calculated width of the microjoint, ie it is not an absolute value. In this way, the calculated minimum microjoint widths for the different workpiece parts of a workpiece change relatively and not absolutely, which prevents small workpiece parts from being connected with an oversized microjoint.

Another aspect of the invention relates to a method for determining an attachment position of a microjoint, by means of which a workpiece part remains connected to a remaining workpiece of an in particular plate-shaped workpiece, comprising: determining a minimum width of the microjoint at several different attachment positions along an outer contour of the workpiece part, with the minimum Width is determined according to the method described above, as well as selecting that approach position along the outer contour for machining the workpiece for which the smallest minimum width of the microjoint was determined. The determination of the minimum width of the microjoint described above is carried out in this case for different attachment positions along the outer contour in order to determine at which point or at which attachment position the microjoint would assume the smallest width. In the programming system for creating the control program for the processing machine, this point can then be automatically selected as the attachment position of the microjoint.

A further aspect of the invention relates to a method of the type mentioned at the outset for processing a particularly plate-shaped workpiece, in which the at least one microjoint is formed at an attachment position along an outer contour of the workpiece part that was determined according to the method described above for determining the attachment position. As described above, an attachment position is selected along the outer contour at which the microjoint has a minimum width.

The invention also relates to a computer program product which is designed to carry out all the steps of the method described above when the computer program runs on a data processing system. The data processing system can in particular be a programming system, i.e. a computer for programming the control programs for a numerical control device of a processing machine, e.g. for cutting processing and / or for transporting a workpiece or a machine arrangement with such a processing machine. If the computer program runs in the programming system, a machining program is generated which, among other things, has a sequence of (control) commands for machining the workpiece. The machining program generated in this way can then be executed by a numerical control device of the processing machine or a machine arrangement containing this processing machine.

Further advantages of the invention emerge from the description and the drawing. The features mentioned above and those listed below can also be used individually or collectively in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather have an exemplary character for describing the invention.

• 1 eine schematische Darstellung einer Bearbeitungsmaschine in Form einer Laserschneidmaschine zum trennenden Bearbeiten eines plattenförmigen Werkstücks,
• 2a,b schematische Darstellungen eines Werkstückteils, das über einen Microjoint mit einem Restwerkstück verbunden ist, beim Verkippen aufgrund eines Gasdrucks eines Schneidgases,
• 3 eine schematische Darstellung einer Bearbeitungsmaschine in Form einer kombinierten Laser- und Stanzmaschine, sowie
• 4a,b Darstellungen eines Werkstückteils, das über einen Microjoint mit einem Restwerkstück verbunden ist, beim Verschieben entlang einer Werkstückauflage.

Show it:

• 1 a schematic representation of a processing machine in the form of a laser cutting machine for the separating processing of a plate-shaped workpiece,
• 2a, b schematic representations of a workpiece part, which is connected to a remaining workpiece via a microjoint, when tilting due to the gas pressure of a cutting gas,
• 3 a schematic representation of a processing machine in the form of a combined laser and punching machine, as well as
• 4a, b Representations of a workpiece part, which is connected to a remaining workpiece via a microjoint, when moving along a workpiece support.

In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

1 shows a CO ₂ laser cutting machine 1 for laser cutting with a CO ₂ laser resonator 2, a laser processing head 4th and a workpiece support 5 . One from the laser resonator 2 generated laser beam 6th is by means of a beam guide 3 from deflection mirrors (not shown) to the laser processing head 4th guided and focused in this and with the help of mirrors, also not shown, perpendicular to the surface 8a of a workpiece 8th aligned, ie the beam axis (optical axis) of the laser beam 6th runs perpendicular to the workpiece 8th .

For laser cutting the workpiece 8th is with the laser beam 6th first pierced, ie the workpiece 8th is melted or oxidized at one point and the resulting melt is blown out. Below is the laser beam 6th over the workpiece 8th moved so that a continuous kerf 9 arises along which the laser beam 6th the workpiece 8th severed.

Both piercing and laser cutting can be supported by adding a gas. As cutting gases 10 oxygen, nitrogen, compressed air and / or application-specific gases can be used. Which gas is ultimately used depends on which materials are cut and which quality demands on the workpiece 8th be asked. Resulting particles and gases can be removed with the help of a suction device 11 from a suction chamber 12th be sucked off. A programmable numerical control device shown schematically 13th controls all essential functions of the laser cutting machine 1 , for example the movement of the laser processing head 4th if a machining program is being executed on this.

2a, b show the separating machining of the workpiece 8th , more precisely a rectangular workpiece part 14th , which along a cutting contour 9 from a leftover workpiece 15th (Scrap skeleton) is separated. The workpiece part remains in the separating process 14th on its outer contour P via a microjoint 17th with the remaining workpiece 15th tied together. The in 2a, b The example shown is the microjoint 17th at a microjoint position m along the outer contour P in the XY plane (the workpiece plane), which does not correspond to a free cutting position f along the outer contour P, which is the end of the cut during separating machining along the cutting contour 9 forms. At the moment when the cutting contour 9 is closed at the free cutting position f, acts on the workpiece part 14th a gas pressure p of the cutting gas 10 one that consists of a machining nozzle 18th the laser cutting machine 1 exit (cf. 2 B) .

Will be a laser cutting head 4th or the active, pressurized surface of the cutting gas nozzle 18th (see. 2 B) again over an area of the with a microjoint 17th connected workpiece part 14th moves, the microjoint 17th the workpiece part exactly in this area 14th tie up. In this way, the force introduced by the gas pressure p has the smallest leverage to the microjoint 17th and thus also generates the slightest tension.

Depending on how the workpiece part 14th relative to the supporting workpiece support elements 5 is arranged, there can be areas along the cutting contour 9 or along the outer contour P of the workpiece part 14th at which the gas pressure p of the cutting gas 10 at the free cutting position f for tilting the workpiece part 14th relative to the remaining workpiece 15th leads.

In this case, the width B _{MJ of} the microjoint 17th Do not fall below a minimum width B _{MJ, min} at which the standing height of the tilting workpiece part 14th one in 2 B The specified maximum stand-up height hmax shown has been reached. The maximum standing height hmax is correct for the in 2a, b shown example with the distance A between the processing nozzle 18th and the remainder of the workpiece 15th or the workpiece 8th match. This definition of the maximum standing height hmax can cause a collision of the workpiece part standing up 14th with the processing nozzle 18th of the laser cutting head 4th be prevented. The distance A between the face of the machining nozzle 18th and the top 8a of the workpiece 8th in the example shown is less than approx. 2 mm, usually 1 mm or less.

• Als Auflagestegkonfiguration S wird die Menge aller Punkte in der XY-Ebene bezeichnet, die durch die Spitzen der Auflagestege 5 gegeben sind, die in 2a durch in X-Richtung verlaufende gepunktete Linien dargestellt sind. Gegeben sind weiterhin die zu schneidende Außenkontur P des Werkstückteil 14, die Microjoint-Position m und die Freischneideposition f entlang der zu schneidenden Außenkontur P.

The calculation or determination of the minimum microjoint width B _{MJ, min} , which must not be undershot, to avoid a collision of the upright workpiece part 14th with the processing nozzle 18th to prevent the in 2a, b The example shown is carried out as described below:

• The support web configuration S is the set of all points in the XY plane that are defined by the tips of the support webs 5 are given in 2a are represented by dotted lines running in the X direction. The outer contour P of the workpiece part to be cut is also given 14th , the microjoint position m and the free cutting position f along the outer contour P to be cut.

The in 2a The hatched area I represents the intersection of the interior of the outer contour P with the support web configuration S, combined with the microjoint position m. The support polygon A shown in dash-dotted lines represents the convex envelope of I. D denotes that side of the support polygon A which is arranged closest to the free cutting position f. The distance between the side D and the free cutting position f is denoted by d. The distance between a position q, which lies on the other side of D with respect to the free cutting position f and has the greatest distance from D, is denoted by e. The force acting on the inside of the outer contour P at the free cutting position f, which is caused by the gas pressure p des from the machining nozzle 18th escaping cutting gas 10 arises is denoted by F in the following.

Using the sizes described above, the minimum width B _{BJ, min of} the microjoint 17th can be determined: Does the force F described above and caused by the gas pressure p act on the workpiece part that has been cut free 14th , this tilts around the axis D.

As a first approximation, the tilt angle α of the workpiece part is 14th about the axis D directly proportional to F * d, so that with a material- _{dependent constant c 0 it} applies that the maximum tilt angle amax in degrees W (P, S, f, m) = max (90; c ₀ * F * d) amounts to.

wobei B_MJ die Breite des Microjoints 17 im Punkt m bezeichnet.It was also found experimentally that 1 / α is directly proportional to the cube of _{the width B MJ of the microjoint} 17th is at the microjoint position m. Hence for a material-dependent constant c: $$\text{W.}\left(\text{P.}\text{, S.}\text{, f}\text{, m}\right)=\text{Max}\left({\text{90; c * F * d / B}}_{\text{MJ}}{}^{\text{3}}\right)\text{,}$$

where B _{MJ is} the width of the microjoint 17th referred to in point m.

kleiner ist als ein vorgegebener Wert hmax, der als maximale Verkipphöhe erlaubt ist, dass also gilt $$\text{H}\left(\text{P},\mathrm{\alpha }\right)<{\text{h}}_{\text{max}}.$$

At a given tilt angle α, it should be ensured according to the invention that the standing height $$\text{H}\left(\text{P.},\mathrm{\alpha }\right)=\text{sin}\left(\mathrm{\alpha }\right)\text{e}$$

is smaller than a predetermined value hmax, which is permitted as the maximum tilting height, that is, that applies $$\text{H}\left(\text{P.},\mathrm{\alpha }\right)<{\text{H}}_{\text{Max}}.$$

Ist e < h_max, kann also das Werkstückteil 14 grundsätzlich zu hoch aufstehen, ergibt sich somit als Bedingung:
sin(c*F*d/B_MJ ³) < h_Max/ e, was genau dann gilt, wenn
c* F*d/B_MJ ³ < arcsin(h_Max/e), was genau dann gilt, wenn $$B_{MJ}>\sqrt[3]{cFd/arcsin\left(\frac{h_{max}}{e}\right)}$$

This condition is met if $$\begin{array}{l}\text{sin}\left(\mathrm{\alpha }\right)\text{e}<{\text{H}}_{\text{Max}},\text{so}\\ (\text{sin}\left(\text{W.}\left(\text{P.}\text{, S.}\text{, p}\text{, m}\right)\right)\text{e}<{\text{H}}_{\text{Max}},\text{so}\\ (\text{sin}\left(\text{Max}\left({\text{90; c * F * d / B}}_{\text{MJ}}{}^{\text{3}}\right)\right)\text{e}<{\text{H}}_{\text{Max}}\text{.}\end{array}$$

If e <h _max , the workpiece part can 14th standing up too high in principle results in the following condition:
sin (c * F * d / B _MJ ³ ) <h _Max / e, which is true if and only if
c * F * d / B _MJ ³ <arcsin (h _Max / e), which is true if and only if $${\mathrm{B.}}_{\mathrm{M.}J}>\sqrt[3]{c\mathrm{F.}d/arcsin\left(\frac{H_{max}}{e}\right)}$$

Due to this inequality, the width B is _{MJ of} the microjoint 17th and thus also the minimum width B _{MJ, min of} the microjoint 17th set.

The minimum width B _{MJ, min of} the microjoint 17th , which was determined in the manner described above, is used in a programming system for the creation of a control program for machining the workpiece 8th used to generate a machining program which is run on the numerical control device 13th when machining the workpiece 8th expires.

The minimum width B _{MJ, min of} the microjoint 17th can be determined as a machining parameter not only as a function of the cutting gas pressure p, but also as a function of other machining parameters that occur when machining the workpiece 8th a relative position of the workpiece part 14th to the Remaining workpiece 15th influence. This is for example when manipulating, more precisely when moving a workpiece 8th the case, as shown below using a combined laser and punching machine 20th which is described in 3 is shown.

The machine tool designed as a laser and punching machine 20th has as machining tools for the separating machining of a plate-shaped workpiece 8th a conventional punching head in the form of a sheet metal 21 with punch 21a and a laser processing head 4th on. The workpiece to be machined 8th stored on a workpiece support during workpiece machining 5 in the form of a processing table. By means of a conventional holding device 22nd what terminals 23 to hold the workpiece 8th has, the workpiece 8th opposite the punch 21a and the laser processing head 4th in the X direction of the workpiece plane (XY plane of an XYZ coordinate system) by means of a conventional linear drive indicated by an arrow 23a be moved. The workpiece can be in the Y-direction of the workpiece plane 8th be moved by the workpiece support 5 together with the holding device 22nd relative to a base 24 on which the workpiece support 5 is mounted, by means of a conventional linear drive indicated by an arrow 23b is moved.

The workpiece 8th can in this way be compared to the punch in the X and Y directions 21a and the laser processing head 4th move so that the respective area of the workpiece to be machined 8th in a stationary processing area 25th of the punch 21a or a stationary processing area 26th of the laser processing head 4th can be positioned. In the editing area 25th of the punch 21 is a (exchangeable) punching die 27 positioned that one opening 27a for engagement for the (also exchangeable) punch 21a having. Correspondingly is in the stationary processing area 26th of the laser processing head 4th a laser die 28 arranged, which as an opening restriction for a substantially circular suction opening 26a in the workpiece support 5 serves. The part of the workpiece support 5 in the X direction at which the machining areas 25th , 26th are formed, is here stationary and is not in the Y-direction relative to the base 24 postponed. The laser processing head 4th can perform a movement in the X- and Y-direction, which through the suction opening 26a is limited. In the 3 shown machine tool 20th also has a control device 13th on that to control the linear drives 23a , 23b in the X direction or in the Y direction of the machine tool 20th serves.

4a, b show a workpiece part 14th , which is via a microjoint 17th on a remaining workpiece 15th is held. When moving the through the microjoint 17th held workpiece part 14th on or along the workpiece support 5 in the X direction acts on the workpiece part 14th the weight F _G in the Z direction when the workpiece part 14th an unsupported area of the workpiece support 5 run over. In addition, the workpiece part 14th in the XY plane around the microjoint 17th bent. The minimum width B _{BJ, min of} the microjoint 17th is therefore also due to the fact that the bend is not so strong that the workpiece part 14th under or over the remaining workpiece 15th slips.

• Vorteilhaft ist der Microjoint 17 an einer Stelle (Microjoint-Position bzw. Ansatzposition m) am Werkstückteil 14 angebracht, an der sich die Hauptträgheitsachse des Werkstückteils 14 mit der Außenkontur P schneidet (z.B. an einer Symmetrieachse des Werkstückteils 14 - abweichend von der in 4a,b gezeigten Darstellung). Auf diese Weise entfällt eine Torsionsbeanspruchung des Microjoints 17 durch die Gewichtskraft F_G. Befindet sich der Microjoint 17 zusätzlich an einer Position m entlang der Außenkontur P, die sich durch Projektion des Schwerpunkts S des Werkstückteils 14 in Richtung der Relativbewegung zwischen Werkstückteil 14 und Werkstückauflage 5 ergibt, entfällt eine weitere Biegebelastung durch die Beschleunigungs- und Reibkraft in einer zweiten Achsrichtung.

The calculation of the minimum microjoint width B _{BJ, min} is based on the position m of the microjoint on the workpiece part 14th addicted:

• The microjoint is advantageous 17th at one point (microjoint position or attachment position m) on the workpiece part 14th attached to which the main axis of inertia of the workpiece part 14th intersects with the outer contour P (e.g. on an axis of symmetry of the workpiece part 14th - different from the in 4a, b illustration shown). In this way, there is no torsional stress on the microjoint 17th by the weight F _G. Is the microjoint 17th additionally at a position m along the outer contour P, which is determined by the projection of the center of gravity S of the workpiece part 14th in the direction of the relative movement between the workpiece part 14th and workpiece support 5 results, there is no further bending load due to the acceleration and frictional force in a second axial direction.

In addition, the microjoint 17th be attached to that point of intersection of the main axis of inertia with the outer contour P, which is the center of gravity S of the workpiece part 14th has the smallest distance, or in that axial direction (X or Y) in which on the workpiece part 14th the greatest acceleration is effective.

• • In Z-Richtung wirkt die Gewichtskraft F_G des Werkstückteils 14, die am Massenmittelpunkt (Schwerpunkt S) angreift.
• • In X- und Y-Richtung wirken eine (Achs-)Beschleunigung a_x, a_Y und eine Haftreibung auf den Microjoint 17
• • Die Kräfte greifen am Schwerpunkt S an, dabei ist ein kleiner Hebel (= Abstand Schwerpunkt S - Ansatzposition m des Microjoints 17) günstig. Dies legt die bevorzugte Ansatzposition m des Microjoints 17 am Werkstückteil 14 fest.
• • Der Microjoint 17 liegt auf einer der Hauptträgheitsachsen.
• • Beim Laserschneiden wird der Microjoint 17 am Schnittende gesetzt, so dass der Gasdruck eine untergeordnete Rolle spielt und vernachlässigt werden kann.

The following assumptions apply to the design of the minimum necessary microjoint width B _{BJ, min described below:}

• _{• The weight F G of} the workpiece part acts in the Z direction 14th that attacks at the center of mass (center of gravity S).
• • An (axial) acceleration a _x , a _Y and static friction act on the microjoint 17 in the X and Y directions
• • The forces act on the center of gravity S, there is a small lever (= distance between the center of gravity S and the attachment position m of the microjoint 17th ) cheap. This sets the preferred attachment position m of the microjoint 17th on the workpiece part 14th fixed.
• • The microjoint 17th lies on one of the main axes of inertia.
• • When laser cutting, the microjoint 17th set at the end of the cut so that the gas pressure plays a subordinate role and can be neglected.

• • Geometrische Eigenschaften des Werkstückteils 14:
  • ◯ Schwerpunkt S des Werkstückteils 14
  • ◯ Ansatzpunkt m des Microjoints 17: liegt optimaler Weise auf einer der Hauptträgheitsachsen des Werkstückteils 14, die einer jeweiligen Symmetrieachse des Werkstückteils 14 entsprechen (falls vorhanden)
• • Materialeigenschaften:
  • ◯ Blechdicke d
  • ◯ zulässige Spannung Bges
  • ◯ E-Modul
  • ◯ Dichte (Gewicht bzw. Masse m)
  • ◯ Reibwert bzw. Reibungskoeffizient µ mit der Werkstückauflage 5
• • Achsparameter der Werkzeugmaschine 20:
  • o Beschleunigung a_X, a_Y in X- und Y-Richtung

For the calculation of the minimum necessary microjoint width B _{BJ, min} under the above assumptions, the following sizes are required:

• • Geometrical properties of the workpiece part 14th :
  • ◯ Center of gravity S of the workpiece part 14
  • ◯ Starting point m of the microjoint 17th : optimally lies on one of the main axes of inertia of the workpiece part 14th , that of a respective axis of symmetry of the workpiece part 14th correspond (if present)
• • Material properties:
  • ◯ sheet thickness d
  • ◯ permissible voltage Bges
  • ◯ modulus of elasticity
  • ◯ Density (weight or mass m)
  • ◯ Coefficient of friction or coefficient of friction µ with the workpiece support 5
• • Axis parameters of the machine tool 20th :
  • o Acceleration a _X , a _Y in the X and Y directions

The microjoint 17th is assumed below as a bending beam on which the following moments act:

Moment in the direction of gravity (around the X axis): $${\mathrm{M.}}_{\text{x}}={\mathrm{F.}}_{\text{G}}\ast {\text{H}}_{\text{y}}\text{with}{\mathrm{F.}}_{\text{G}}=m\ast G$$

mit $$F_{\text{ax}}=m\ast a_{\text{x}}\text{ und }{F}_{\text{ay}}=m\ast a_{\text{y}}{\text{ und F}}_{\text{R}}={\text{F}}_{\text{G}}\ast \mathrm{\mu },$$

mit den nachfolgenden Bezeichnungen: m = Masse des Werkstückteils, g = Erdbeschleunigung, h_x = Abstand Schwerpunkt S zum Ansatzpunkt m des Microjoints 17 in X-Richtung, h_y = Abstand Schwerpunkt S zum Ansatzpunkt m des Microjoints in Y-Richtung, a_x = Beschleunigung in X-Richtung, a_y = Beschleunigung in Y-Richtung, µ = Reibungskoeffizient zwischen dem Material des Werkstückteils 14 und der Werkstückauflage 5.Moment in X and Y directions (around the Z axis): $${\mathrm{M.}}_{\text{z}}=\left({\mathrm{F.}}_{\text{ax}}+{\mathrm{F.}}_{\text{R.}}\right)\ast {\text{H}}_{\text{y}}\text{+}\left({\mathrm{F.}}_{\text{ay}}+{\mathrm{F.}}_{\text{R.}}\right)\ast {\text{H}}_{\text{x}}$$

with $${\mathrm{F.}}_{\text{ax}}=m\ast a_{\text{x}}\text{and}{\mathrm{F.}}_{\text{ay}}=m\ast a_{\text{y}}{\text{and F}}_{\text{R.}}={\text{F.}}_{\text{G}}\ast \mathrm{\mu },$$

with the following designations: m = mass of the workpiece part, g = acceleration due to gravity, h _x = distance from the center of gravity S to the starting point m of the microjoint 17th in the X direction, h _y = distance from the center of gravity S to the starting point m of the microjoint in the Y direction, a _x = acceleration in the X direction, a _y = acceleration in the Y direction, µ = coefficient of friction between the material of the workpiece part 14th and the workpiece support 5 .

The in 4a, b shown example in which the workpiece part 14th is only shifted in the X-direction, the frictional force F _R does not apply in the Y-direction. The moment around the Y-axis is omitted due to the simplification that the microjoint 17th lies on one of the main axes of inertia.

$$\begin{array}{cc}{W}_{\text{z}}=I_{\text{z}}\text{/}\left({\text{B}}_{\text{MJ}}\text{/}2\right)& mit{I}_{\text{z}}=\left(\text{d}\ast {\text{B}}_{\text{MJ}}{}^3\right)\text{/}12\end{array}$$

(d=Werkstückdicke, B_MJ = Microjoint-Breite)Determination of the moment of resistance W _X , W _{Y of the microjoint} 17th : $$\begin{array}{cc}{\mathrm{W.}}_{\text{x}}={\mathrm{I.}}_{\text{x}}\text{/}\left(d\text{/}2\right)& mit{\mathrm{I.}}_{\text{x}}=\left({\text{B.}}_{\text{MJ}}\ast {\text{d}}^3\right)\text{/}\mathrm{12th}\end{array}$$

$$\begin{array}{cc}{\mathrm{W.}}_{\text{z}}={\mathrm{I.}}_{\text{z}}\text{/}\left({\text{B.}}_{\text{MJ}}\text{/}2\right)& mit{\mathrm{I.}}_{\text{z}}=\left(\text{d}\ast {\text{B.}}_{\text{MJ}}{}^3\right)\text{/}\mathrm{12th}\end{array}$$

(d = workpiece _{thickness, B MJ} = microjoint width)

$${\text{B}}_{\text{z}}={\text{M}}_{\text{z}}{\text{/W}}_{\text{z}}$$

$$\Rightarrow {\text{B}}_{\text{ges}}={\text{B}}_{\text{x}}+{\text{B}}_{\text{z}}\left(\text{vektorielle Addition}\right)$$

The bending stress Bges at the microjoint can be derived from this 17th to calculate: $${\text{B.}}_{\text{x}}={\text{M.}}_{\text{x}}{\text{/ W}}_{\text{X}}$$

$${\text{B.}}_{\text{z}}={\text{M.}}_{\text{z}}{\text{/ W}}_{\text{z}}$$

$$\Rightarrow {\text{B.}}_{\text{total}}={\text{B.}}_{\text{x}}+{\text{B.}}_{\text{z}}\left(\text{vector addition}\right)$$

The microjoint width B _BJ must be selected so that the bending stress Bges is at most as large as the yield point R _p0.2 for the material of the currently displaced workpiece 8th : $${\text{B.}}_{\text{total}\text{,Max}}\le {\text{R.}}_{\text{p}0.2}$$

$$\text{mit }a=-R_{p\mathrm{0,2}};b=\frac{6\left|h_y\right|\cdot F_G}{d^2};c=\frac{6\left(\left|h_x\right|\cdot F_{ay}+\left|h_y\right|\cdot \left(F_{ax}+F_R\right)\right)}{d}$$

und schließlich: $$B_{MJ,minB}=\text{max}\left\{B_{MJ1},B_{MJ2}\right\}$$

The minimum microjoint width B _{MJ, minB} is then calculated for this predetermined limit value R _{p0.2 of} the voltage B _{tot, max} as follows: $${\mathrm{<figure-callout\; id="2"\; label="B.\; m\; j"\; filenames="DE102020205680A1\_0019.png"\; state="\{\{state\}\}">B.</figure-callout>}}_{mj}=\frac{-b\pm \sqrt{b^2-\mathrm{4th}ac}}{2a}$$

$$\text{with}a=-{\mathrm{R.}}_{p0.2};b=\frac{\mathrm{6th}\left|H_y\right|\cdot {\mathrm{<figure-callout\; id="2"\; label="F.\; G\; d"\; filenames="DE102020205680A1\_0019.png"\; state="\{\{state\}\}">F.</figure-callout>}}_G}{d^{}};c=\frac{\mathrm{6th}\left(\left|H_x\right|\cdot {\mathrm{F.}}_{ay}+\left|H_y\right|\cdot \left({\mathrm{F.}}_{ax}+{\mathrm{F.}}_{\mathrm{R.}}\right)\right)}{d}$$

and finally: $${\mathrm{B.}}_{\mathrm{M.}J,min\mathrm{B.}}=\text{Max}\left\{{\mathrm{B.}}_{\mathrm{M.}J1},{\mathrm{B.}}_{\mathrm{M.}J2}\right\}$$

The minimum microjoint width B _{BJ, minB} is the maximum of the two values B _MJ1 , B _MJ2 because the smaller of the two values is always negative due to the root used in the calculation.

An empirically determined safety factor c _{1 can be} added to the calculated minimum microjoint width B _{BJ, minB, which reduces} the influence of external disturbance variables, such as vibrations during the punching process, sagging of the workpiece part 14th , Deflection of the workpiece part 14th taken into account when driving over support elements (e.g. balls or brushes), ie B _{BJ, min} = BBJ, minB + C1 applies.

In addition, the safety factor c ₁ at the attachment position m of the microjoint 17th occurring notch effect due to the sudden diameter reduction must be taken into account, which leads to a reduction in the maximum allowable bending stress B _{tot, max} . The safety factor c ₁ is ideally dependent on the calculated microjoint width (c ₁ (B _{BJ, minB} )), ie it is not an absolute value. In this way, the calculated minimum microjoint widths B _{BJ, min change} for the different workpiece parts 14th a workpiece 4th relative and not absolute, which prevents small workpiece parts 14th with an oversized microjoint 17th be connected.

Both that in connection with 2a, b as well as that in connection with 4a, b described method for determining the minimum width B _{BJ, min of} the microjoint 17th is typically for several different approach positions m along the outer contour P of the workpiece part 14th carried out. For machining the workpiece 8th that approach position m along the outer contour P is selected for which the smallest minimum width B _{BJ, min of} the microjoint 17th was determined. During the subsequent machining of the workpiece 8th will be the at least one microjoint 17th through which the workpiece part 14th with the remaining workpiece 15th remains connected, formed at the approach position m selected in the manner described above and with the minimum width B _{BJ, min} determined in the manner described above.

The minimum width B _{BJ, min} and the attachment position m of the microjoint 17th are used in a programming system to create a control program or to create control commands for machining the workpiece 8th used. The control program created in this way is used by the control device 13th when machining the workpiece 8th processed. The programming system contains workpiece information and machining parameters for machining the workpiece 8th stored, which are used to determine the minimum width B _{BJ, min of} the microjoint 17th are required, for example the cutting gas pressure p when machining the workpiece 8th or the axis accelerations a _x , a _Y when moving the workpiece 8th along the workpiece support 5 . It goes without saying that, as an alternative or in addition to the machining parameters described above, other machining parameters can be used to _{determine the minimum width B BJ, min of the microjoint} 17th can be used, which shows the relative position of the (at least one) microjoint 17th with the remaining workpiece 15th connected workpiece part 14th in relation to the remaining workpiece 15th or in relation to the workpiece support 5 influence.

Claims (11)

A method for determining a minimum width (B _{MJ, min)} of a microjoints (17), with a remainder of the workpiece (15) of the workpiece (8) is connected through which a workpiece part (14) when processing a particular plate-shaped workpiece (8), characterized that the minimum width (B _{MJ, min} ) of the microjoint (17) is determined as a function of at least one machining parameter (p, a _x , a _Y ) which, when machining the workpiece (8), defines a relative position of the workpiece part (14) influenced to the remaining workpiece (15). Procedure according to Claim 1 , in which the machining of the workpiece (8) comprises thermal cutting of the workpiece (8) with a machining beam, in particular with a laser beam (6), the minimum width (B _{MJ, min} ) of the microjoint (17) depending on a machining parameter in the form of a gas pressure (p) of a cutting gas (10) exiting from a machining nozzle (18) acting on the workpiece part (14) at the moment the workpiece part (14) is cut free from the remaining workpiece (15). Procedure according to Claim 2 , at which a minimum width (B _{MJ, min} ) of the microjoint (17) is determined, at which when the workpiece part (14) tilts relative to the remaining workpiece (15 ) a maximum standing height (hmax) with which the workpiece part (14) protrudes over the remaining workpiece (15) is not exceeded. Procedure according to Claim 3 , at which the maximum standing height (hmax) is not greater than a distance (A) between the processing nozzle (18) and the remaining workpiece (15), the distance (A) preferably less than 2 mm, particularly preferably less than 1 mm lies. Method according to one of the preceding claims, in which the machining of the workpiece (8) comprises moving the remaining workpiece (15) together with the workpiece part (14) along a workpiece support (5), the minimum width (B _{MJ, min} ) of the microjoint (17) is determined as a function of at least one machining parameter in the form of an acceleration (a _x , a _Y ) of the workpiece part (14) during displacement along at least one displacement direction (X, Y). Procedure according to Claim 5 , in which a minimum width (B _{BJ, minB} ) of the microjoint (17) is determined, in which when the workpiece part (14) is moved together with the remaining workpiece (15), a bending stress on the microjoint (17) results in a maximum bending stress (B _{tot , max} ). Procedure according to Claim 6 , at which the maximum bending stress (B _{tot, max} ) at the microjoint (17) is not greater than a yield point (R _p0.2 ) of the material of the workpiece (8). Procedure according to Claim 6 or 7th , in which the minimum width (B _{BJ, min} ) of the microjoint (17) is derived from the minimum width (B _{BJ, minB} ) of the microjoint (17) at which the maximum bending stress (B _{tot, max} ) is not exceeded, and composed of a safety factor (c ₁ ), the safety factor (c ₁ ) preferably depending on the minimum width (B _{BJ, min, B} ) of the microjoint (17) at which the maximum bending stress (B _{tot, max} ) is not exceeded will. A method for determining an attachment position (m) of a microjoint (17), by means of which a workpiece part (14) remains connected to a remaining workpiece (15) when processing an in particular plate-shaped workpiece (8), comprising: determining a minimum width (B _{BJ, min} ) of the microjoint (17) at several different attachment positions (m) along an outer contour (P) of the workpiece part (14), the minimum width (B _{BJ, min} ) being determined according to the method according to one of the preceding claims, as well as selecting that attachment position (m) along the outer contour (P) for machining the workpiece (8), for which the smallest minimum width (B _{BJ, min} ) of the microjoint (17) was determined. A method for processing an in particular plate-shaped workpiece (8), comprising: processing the workpiece (8) with the formation of at least one microjoint (17) through which a workpiece part (14) remains connected to a remaining workpiece (15), characterized in that the at least a microjoint (17) is formed at an attachment position (m) along an outer contour (P) of the workpiece part (14), which according to the method according to Claim 9 was determined. Computer program product which is designed to carry out all steps of the method according to one of the preceding claims when the computer program runs on a data processing system.

Images